The field of this invention is patient monitoring systems.
Frequent monitoring of patients permits the patients"" physician to detect worsening symptoms as they begin to occur, rather than waiting until a critical condition has been reached. As such, home monitoring of patients with chronic conditions is becoming increasingly popular in the health care industry for the array of benefits it has the potential to provide. Potential benefits of home monitoring are numerous and include: better tracking and management of chronic disease conditions, earlier detection of changes in the patient condition, and reduction of overall health care expenses associated with long term disease management. The home monitoring of a number of diverse xe2x80x9cchronic diseasesxe2x80x9d is of interest, where such diseases include diabetes, dietary disorders such as anorexia and obesity, respiratory diseases, AIDS and other chronic viral conditions, conditions associated with the long term use of immunosuppressants, e.g. in transplant patients, asthma, chronic hypertension, chronic use of anticoagulants, and the like.
Of particular interest in the home monitoring sector of the health care industry is the remote monitoring of patients with heart failure (HF), also known as congestive heart failure. HF is a syndrome in which the heart is unable to efficiently pump blood to the vital organs. Most instances of HF occur because of a decreased myocardial capacity to contract (systolic dysfunction). However, HF can also result when an increased pressure-stroke-volume load is imposed on the heart, such as when the heart is unable to expand sufficiently during diastole to accommodate the ventricular volume, causing an increased pressure load (diasystolic dysfunction). In either case, HF is characterized by diminished cardiac output and/or damming back of blood in the venous system. In HF, there is a shift in the cardiac function curve and an increase in blood volume caused in part by fluid retention by the kidneys. Indeed, many of the significant morphologic changes encountered in HF are distant from the heart and are produced by the hypoxic and congestive effects of the failing circulation upon other organs and tissues. One of the major symptoms of HF is edema, which has been defined as the excessive accumulation of interstitial fluid, either localized or generalized.
Edema is defined as the abnormal accumulation of fluid in connective tissue. Edema typically results from a combination of passive venous congestion and salt and water retention, and may be systemic or localized to a particular region of the body. Dependent edema, in which fluid accumulates in the tissues of the limbic extremities, e.g. ankle, foot and the like, is a physical manifestation of a number of different human disease conditions. Dependent edema first appears in the feet and ankles of the ambulatory patient, and in the posterior surface of the calves and skin overlying the sacrum in the bedridden patient. Disease conditions characterized by the presence of dependent edema include local venous or lymphatic obstruction, cirrhosis, hypoalbumenia, and congestive heart failure.
In congestive heart failure, the presence of edema in the lower extremities is a valuable diagnostic marker for the presence of the disease. In addition to serving as a marker for the presence of congestive heart failure, the progression of the edemic state can be monitored over time and the progression of the edemic state related to the progression of the disease.
One way of detecting the presence of edema is to determine fluid volume change of the patient. A number of different technologies have been developed to identify the volume change, and include those based on the use of water or air-filled cuffs, mercury strain gauge, fiber optic strain gauge, and airborne ultrasound. Such technologies have principally been employed to measure venous blood flow and to sense the volume pulsations created by the heart.
Another way of detecting the presence of edema is the xe2x80x9cpittingxe2x80x9d method. In this method, a physician""s thumb or finger is pressed into the patient""s skin next to a bony surface (e.g., tibia, fibula, or sacrum). When the physician""s finger is withdrawn, an indentation persists for a short time. The depth of the xe2x80x9cpitxe2x80x9d is estimated and generally recorded in millimeters, although subjective grading systems (e.g. xe2x80x9c+++xe2x80x9d, etc.) have also been described. In general, the distribution of edema is also noted, as the amount of fluid is roughly proportional to the extent and the thickness of the pit.
HF is the most common indication for hospitalization among adults over 65 years of age, and the rate of admission for this condition has increased progressively over the past two decades. It has been estimated that HF affects more than 3 million patients in the U.S. (J. B. O""Connell et al., J. Heart Lung Transpl. (1993) 13(4):S107-112).
In the conventional management of HF patients, where help is sought only in crisis, a cycle occurs where patients fail to recognize early symptoms and do not seek timely help from their care-givers, leading to emergency department admissions (Miller, P. Z., 1995, xe2x80x9cHome monitoring for congestive heart failure patients, xe2x80x9d Caring Magazine, August 1995: 53-54). Recently, a prospective, randomized trial of 282 patients was conducted to assess the effect of the intervention on the rate of admission, quality of life, and cost of medical care. In this study, a nurse-directed, multi disciplinary intervention (which consisted of comprehensive education of the patient and family, diet, social-service consultation and planning, review of medications, and intensive assessment of patient condition and follow-up) resulted in fewer readmissions than the conventional treatment group and a concomitant overall decrease in the cost of care (M. W. Rich et al., New Engl. J. Med. (1995) 333:1190-95). Similarly, comprehensive discharge planning and a home follow-up program was shown to decrease the number of readmissions and total hospital charges in an elderly population (M. Naylor et al., Amer. College Physicians (1994) 120:999-1006). Therefore, home monitoring is of particular interest in the HF management segment of the health care industry.
Another area in which home-monitoring is of particular interest is in the remote monitoring of a patient parameter that provides information on the titration of a drug, particularly with drugs that have a consequential effect following administration, such as insulin, anticoagulants, ACE inhibitors, xcex2-blockers, etc.
Although a number of different home monitoring systems have been developed, there is continued interest in the development of new monitoring systems. Of particular interest would be the development of a system that provides for improved patient compliance, ease of use, etc. Of more particular interest would be the development of such a system that is particularly suited for use in the remote monitoring of patients suffering from HF.
Relevant Literature
Monitoring systems are described in U.S. Pat. Nos. 5,241,965; 5,549,117; 5,584,297; 5,307,263; 4,803,625; 4,546,436; 5,007,429; 5,019,974; 5,077,476; 5,182,707; 4,838,275; as well as in Capone et al., Am. Heart J. (1988) 116: 1606; Chadda et al., Am. Heart J. (1986) 112: 1159; Fleg et al., Arch. Intern. Med. (1989) 149:393; Katz et al., Obstetrics and Gynecology (1986)68:773; Patel et al., J. Med. Sys. (1992) 16: 101.
Scientific American Medicine (Dale and Freeman eds)1:II provides a review of heart failure, physical manifestations and methods for the treatment thereof.
Lindahl and Omata, Med. Biol. Eng. Comput. (1995) 33:27-32 provide a description of methods of assessing edema.
Other references of note include U.S. Pat. Nos.: 3,791,375; 3,890,958; 3,974,491; 4,144,749; 4,383,533; 5,052,405; 5,323,650; and 5, 385,069; as well as Swedborg, Scand. J. Rehab. Med. (1977) 9:131-135; Mridha and Odman, Scand. J. Rehab. Med. (1989)21:63-39; Mridha and xc3x96dman, Med. Biol. Eng. Comput. (1986) 24: 393-398; Kushner et al., Am. J. Clin. Nut. (1986) 44: 417-424; Breytenbach, Int. J. Oral Surg. (1978) 7:386-392; Davies et al., Med. Biol. Eng. Comput. (1971) 9:567-570; Lindhal et al., Med. Biol. Eng. Comput. (1991) 29: 591597; Iwakura, Med. Biol. Eng. Comput. (1978) 16:429-436; and Starr, BPR (1980) 17:98-102.
A patient interface system for collecting and transferring data from a patient to a remote monitoring system, and methods for its use in the management of a chronic condition, are provided. The subject interface system includes: (a) a patient data input means having both a sensor and a question and answer means; (b) a processing means; and (c) a communication means for transferring data to and from a remote monitoring means. Also provided is a patient monitoring system comprising the subject patient interface means operationally linked to the remote monitoring system. The subject patient interface system finds use in a variety of applications in which the condition of a patient is monitored remotely, and is particularly suited for use in the remote monitoring of patients suffering from a cardiac associated disease.
The patient interface system is particularly adapted for measuring edema of a patient on a daily basis. Data obtained from each measurement are transmitted to a central processing location for analysis. The system is designed so that it can receive and process data from a plurality of different patients at a plurality of different locations. The data are analyzed to determine if additional action is needed, e.g., obtain additional data via specific questions posed to the patient(s) and/or instruct the patient(s) to obtain medical assistance.
These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the patient interface system, as more fully described below.